The developmental effects of dark-rearing, rearing under diffused light, rearing with de-correlated visual and motor experience, and rearing under somatosensory deprivation are under investigation. Measures include behavioral, neurophysiological, neuroanatomical, and neurochemical alterations. Hooded rats, cats, and monkeys (Macaca speciosa) are being used in various phases of this work. Cerebellar and cortical areas are being investigated for amino acid turnover rates, changes in dendritic growth and spine counts, differences in evoked potentials as a function of patterned and unpatterned stimulus inputs, and for effects on layer thickness and cell diameters. Behavioral responses that measures visual acuity, various perceptual deficits, and altered rates of discrimination learning are included where feasible and appropriate to questions of function of the visual and somatosensory systems. General responses to novel stimulation, measures of arousal, and behavioral stereotypies are being emphasized in the work with M. speciosa.